Microscopical Society. 73 



iiiing, who have described these bodies to be animals which arc 

 "porous, with skeletons consisting of cartilaginous tubes destitute 

 of earthy spicula," proceeds to state that he was induced to investi- 

 gate this division of the Sponges in consequence of having received 

 from Rupert Kirk, Esq., of Sydney, numerous specimens of Sponges, 

 among which were many exhibiting every appearance of being true 

 Keratose sponges, but which, upon a close examination with a high 

 microscopic power, were discovered to be abundantly furnished with 

 siliceous spicula. The existence of spicula in these specimens led 

 the author to suspect their 2)resence in the keratose sponges of 

 commerce. Upon examining these sponges, there were found to be 

 two well-marked species from the Mediterranean, and a third which 

 is obtained from the West India Islands. The first and commonest 

 species of Mediterranean sponge, is the Spongia officinalis of Lamarck. 

 When examined, before it has been cleaned and bleached by the 

 dealers, with a power of five hundred linear, the fibre from the exte- 

 rior presents the appearance of a smooth, light, amber-coloured thread; 

 but when taken from the interior it is seen to be coated with a thin 

 and somewhat rugose film, containing minute granules, which the 

 author believes to be the incipient gemmules of the sponge, by Avhich 

 the sponge is propagated, after the manner described by Dr. Grant 

 as occurring in other divisions of this class. The greater part of the 

 fibres consist of cylindrical transparent threads, frequently anasto- 

 mosing and varying considerably in their size. This portion of the 

 tissue is destitute of spicula ; but there frequently occur, dispersed 

 amid this form of tissue, large flattened fibres running in a straight 

 direction, and it is in these that spicula are found imbedded in the 

 centre of the tissue. The spicula vary considerably in their size and 

 form, and are best obtained for examination by burning small pieces of 

 the sponge to a white ash, and washing this with dilute muriatic acid. 

 In the other sponges of commerce, spicula are found in equal abun- 

 dance. All the writers who have treated of Spongia officinalis have 

 descrihed it as consisting of horny tubes ; but the author states this 

 to be an error, and proves the thread in all the species of the sponges 

 of commerce to be a solid horny fibre. The second species of Me- 

 diterranean sponge is described as being very similar in its external 

 characters, and in the size, form and arrangement of its fibres, to S. 

 officinalis, but is distinguished from it by the possession of a beauti- 

 ful vascular tissue, which surrounds in great abundance nearly every 

 fibre of its structure, frequently anastomosing and running in every 

 possible direction over its surface. This tissue is not imbedded in 

 the horny mass of the fibre, but is contained in a sheath, which closely 

 embraces it. In one of these vessels the author observed numerous 

 minute globules, exhibiting every appearance of being globules of 

 circulation analogous to those found in the blood of the higher classes 

 of animals. These molecules were extremely minute, the largest 

 being but the 16,666th of an inch in diameter, and the smallest the 

 50,000th of an inch in diameter. A similar vascular tissue is stated 

 to exist in a considerable number of the keratose sponges of Au- 

 stralia. The author concludes by some observations on the nature 



